BMP-2-producing L cells induce osteogenesis in vivo and in vitro

Abstract

A high level of expression of the humanbone morphogenetic protein-2 (hBMP-2) gene was found in L cells under control of a cytomegalovirus enhancer and a chicken β-actin promoter. The induction of osteogenesis in vitro was examined by treating the stromal cell lines MC3T3-E1, ST2, and OP9 with either conditioned medium (CM) from hBMP-2 L cell transfectants, or with retinoic acid. BMP-2 CM induced alkaline phosphatase (ALP) activity in all three cell lines at different levels, with ALP activity in the OP9 cell line being approximately one-tenth that in the other cell lines. Serum induced ALP activity synergistically with BMP-2 CM. Retinoic acid strongly induced ALP activity only in the ST2 cell line. The different responses of stromal cell lines to BMP-2 CM and retinoic acid characterized stromal and preosteoblastic cells. In an in vivo analysis, BMP-2-producing L cells were injected into the foreleg and thigh muscles of nude mice, resulting in ectopic bone formation.